Trust me on this...
If you want your car look cool, do not go for body modifications or headlights and grille from other cars. It will end up looking very weird.
Modify you car for sure, but enhance it's look but keeping it's originality. Please do not try to make a Omni look like another car, it will look like a confused.
For starters, go for a bit fatter tyres and good alloys. Look at how good this van looks -
If you wanna go extreme, you can even lower the ride height or go for low profile tyres. That will look extremely sexy but I will not recommend that because of Indian road conditions.
Make a van look like a van, play with it's strong points. Make it look gangsta! Dont make it look like a confused child of donald duck & mickey mouse.